You need to consider certain factors when you install a drive isolation transformer ahead of a variable speed drive. For example:

  • It may be required by local codes.
  • It provides a "Y" secondary configuration which allows a better ground for the drive system.
  • It will limit the available fault current to the drive.
  • It will limit the impact of electrical disturbances generated by the drive from getting in the power system.
  • It will limit the impact of electrical disturbances coming from the power system.














Using a standard duty motor with a PWM inverter may only produce 80% of the rated torque. Even at that torque, you can expect a 2 to 1 turn down in the speed before losing even more torque. Also, the PWM inverter adds more heating to the standard duty motor and may cause it to fail permanently.













Worm reducers are generally used in low to moderate horsepower applications. They offer low initial cost, high ratios and high output torque in a small space. They have a much higher tolerance to shock loading than helical gear units. Helical reducers are used in higher horsepower applications where long-term operating efficiency is more important than initial cost. They can be furnished in a concentric shaft design when its desirable to have input and output shafts with a common centering.













Dynamic braking is a resistor package that is added to the variable speed drive to absorb excess electrical energy when the motor is acting as a generator. The power sections of AC and DC variable speed drives handle the excess energy increases in different ways depending on the type of drive. With a DC non-regenerative drive system, dynamic braking is only in effect during the stopping mode. The electronics of a DC regenerative drive are such that energy increases flow back into the AC power system all the time. With an AC inverter drive system, dynamic braking is on full-time during running and deceleration.













The "X" belts have a raw edge which increases the frictional grip of the belt in the sheave and generally have higher rated tensile cords. The "cogged" design also allows this style of belt to be run on smaller sheaves.













Chain life is directly dependent on lubrication. Properly lubed chain lasts 8 times longer than non-lubed chain. A good rule of thumb is to make sure that chain has a visible coating of lubrication at all times.













Inductive proximity sensors can only sense metal objects and in that case are the recommended selection from both a cost and operating effectiveness standpoint. Select capactive proximity sensors for sensing non-metallic objects.













An increase in length of 3% or more is a general guideline to determine worn out chain. Measure several 5 or 10-foot sections to determine wear elongation and replace the chain if elongation exceeds 3%.













Base oil viscosity is always a key oil and grease selection factor. Use a thin viscosity grease for motors since the application parameters are high speed at normal to heavy loads. These application conditions also require exceptional mechanical and chemical stability properties in the grease. Bel-Rays’ Termalene Ball and Roller Bearing Grease is an excellent reference product. Too thick a viscosity such as in a general purpose grease will result in grease breakdown and cause unnecessary high re-grease cycles or motor bearing failures.













Introduce mechanical advantage or ratios whenever possible.

Example: Application requires 700/in/lbs. Torque at 90 RPM utilizing 1 HP 1800 RPM motor (36 in/lbs. Torque at 1 HP)

Option 1-- 20:1 gear reducer with 720 in/lbs. output torque capacity. 36 in/lbs. x 20 = 720 in/lbs. capacity less the efficiency factor

Option 2-- 10:1 gear reducer 36 in/lbs. x 10 = 360 capacity plus 2:1 chain drive from reducer output shaft to driven shaft

Option 2 would probably be most economical because we are reducing the gearbox requirement (capacity needed) by half and still maintaining 720 in/lbs. required at driver shaft by using a 2:1 chain drive.

NOTE: The more HP or torque that needs to be transmitted the more money that can be saved by multiplying torque through reducers and chain or belt drives.













Most synthetic lubricants generally have lower pour points, high oscillation resistance, and accept additives better than their conventional petroleum equivalents. Therefore a gearbox in any of the following conditions could benefit from the use of synthetic lubes: hot or cold ambient temperatures; heavy loads; continuous duty; long drain interval periods desired.













A visual inspection should be conducted after three months service and at six-month intervals thereafter.